Piston to Valve clearance check
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Joined: May 2014
Posts: 88
Likes: 4
From: Fort Frances
Piston to Valve clearance check
Hey everyone. To keep it as short as possible Im assembling my 98 that I just got my parts back and Im looking to double check the piston to valve clearance. Details are as follows;
Stock cylinders bored to 3.937
CP BHM98-3(+3cc dome) pistons
Heads ported and worked;
1.9 AV&V Intake
1.61 AV&V Exhaust
AV&V 6000VSK Springs
Shaved 0.040(83.5cc final)
Cometic 0.030 head gasket
Final static compression 10.2:1
S&S 570c cams(Lift @TDC 0.187 Int,0.179 Ex)
Now I know there are plenty of builds out there that are the same or similar with no clearance issues whatsoever, so is checking clearances even worth it?
Either way Ive found conflicting ways to do it, clay is the method of choice but conflicting methods when it comes to torquing and gaskets. Some say just to use some paper in place of gaskets so you dont ruin the ones you plan to use and just to do everything snug(full torque sequence not necessary). Ive also read no gaskets and just snug fit-up, and then Ive also read full torque sequence and proper gaskets(more timely and risk of having to buy more gaskets, but more accurate). Curious your thoughts on this? Thanks
Stock cylinders bored to 3.937
CP BHM98-3(+3cc dome) pistons
Heads ported and worked;
1.9 AV&V Intake
1.61 AV&V Exhaust
AV&V 6000VSK Springs
Shaved 0.040(83.5cc final)
Cometic 0.030 head gasket
Final static compression 10.2:1
S&S 570c cams(Lift @TDC 0.187 Int,0.179 Ex)
Now I know there are plenty of builds out there that are the same or similar with no clearance issues whatsoever, so is checking clearances even worth it?
Either way Ive found conflicting ways to do it, clay is the method of choice but conflicting methods when it comes to torquing and gaskets. Some say just to use some paper in place of gaskets so you dont ruin the ones you plan to use and just to do everything snug(full torque sequence not necessary). Ive also read no gaskets and just snug fit-up, and then Ive also read full torque sequence and proper gaskets(more timely and risk of having to buy more gaskets, but more accurate). Curious your thoughts on this? Thanks
Road Warrior
Joined: Sep 2014
Posts: 1,872
Likes: 1,325
From: DeLand, Florida
I always just put head on without gasket and then add compressed gasket height to clay squashed thickness. It’s easy and give a good measurement.
From a Motortrend article:
Place a piece of modeling clay or Silly Putty on the top of the piston, then bolt the cylinder head to the block. A trick we were told was to install the head without the head gasket. That way you're not compressing a new gasket until you're ready for final installation, plus it gives you a fudge factor of the gasket's compressed thickness. In other words, if the piston to valve clearance is on the close side of good without the gasket, you know you'll be golden with the gasket installed.
From a Motortrend article:
Place a piece of modeling clay or Silly Putty on the top of the piston, then bolt the cylinder head to the block. A trick we were told was to install the head without the head gasket. That way you're not compressing a new gasket until you're ready for final installation, plus it gives you a fudge factor of the gasket's compressed thickness. In other words, if the piston to valve clearance is on the close side of good without the gasket, you know you'll be golden with the gasket installed.
Thread Starter
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Advanced
Joined: May 2014
Posts: 88
Likes: 4
From: Fort Frances
I always just put head on without gasket and then add compressed gasket height to clay squashed thickness. Its easy and give a good measurement.
From a Motortrend article:
Place a piece of modeling clay or Silly Putty on the top of the piston, then bolt the cylinder head to the block. A trick we were told was to install the head without the head gasket. That way you're not compressing a new gasket until you're ready for final installation, plus it gives you a fudge factor of the gasket's compressed thickness. In other words, if the piston to valve clearance is on the close side of good without the gasket, you know you'll be golden with the gasket installed.
From a Motortrend article:
Place a piece of modeling clay or Silly Putty on the top of the piston, then bolt the cylinder head to the block. A trick we were told was to install the head without the head gasket. That way you're not compressing a new gasket until you're ready for final installation, plus it gives you a fudge factor of the gasket's compressed thickness. In other words, if the piston to valve clearance is on the close side of good without the gasket, you know you'll be golden with the gasket installed.
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
Definitely worth taking the time to measure for future reference. Suppose you want to change cams in the future; you have a baseline and you can use the diffeence in TDC lift to verify that the new cam will not be a problem.
I agree with Cobra1. Have cheked V to P clearance many times. No head gasket, MLS head gaskets do not compress, so you can just add the gasket thickness to measured dimensions. I put the clay in the ref for a while, just to stiffen it up a bit; makes it easier to work with after being compressed. If you have any used HD lifters handy, you can convert them to solids. Google is your friend but the basic procedure is to disassemble the lifter and re-assemble without the spring or piddle valve but install the plunger backwards, install the pushrod seat and retainer clip; it's not a solid lifter you can use to check P to V clearance. You need at least .060".
I agree with Cobra1. Have cheked V to P clearance many times. No head gasket, MLS head gaskets do not compress, so you can just add the gasket thickness to measured dimensions. I put the clay in the ref for a while, just to stiffen it up a bit; makes it easier to work with after being compressed. If you have any used HD lifters handy, you can convert them to solids. Google is your friend but the basic procedure is to disassemble the lifter and re-assemble without the spring or piddle valve but install the plunger backwards, install the pushrod seat and retainer clip; it's not a solid lifter you can use to check P to V clearance. You need at least .060".
Last edited by djl; Jun 10, 2023 at 11:57 AM.
Road Master
Joined: Mar 2013
Posts: 817
Likes: 380
From: Central Ohio
IMO, use the gasket and tq to spec. It doesn't take much longer, and gaskets aren't big bucks. I do agree that it should be checked, for reasons like DJL said
I like using gaskets and bolting everything down to spec just so there's no guessing. The valves are at an angle, a .030 gasket won't add .030" of valve clearance
I like using gaskets and bolting everything down to spec just so there's no guessing. The valves are at an angle, a .030 gasket won't add .030" of valve clearance
Seasoned HDF Member
Joined: May 2008
Posts: 21,176
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From: South Carolina
It will vertically.
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Road Master
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From: Central Ohio
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Seasoned HDF Member
Joined: Oct 2019
Posts: 10,809
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From: OH
[QUOTE=LIVINtheLIFE;21249788
Now I know there are plenty of builds out there that are the same or similar with no clearance issues whatsoever, /QUOTE]
FWIW: I have virtually the same specs.
I believe you will be pleased with the results
Now I know there are plenty of builds out there that are the same or similar with no clearance issues whatsoever, /QUOTE]
FWIW: I have virtually the same specs.
I believe you will be pleased with the results
Grand HDF Member
Joined: May 2014
Posts: 3,844
Likes: 1,174
From: florida
definitely measure it.
i make solid lifters as well.
i use old gaskets when i am measuring, but i have them at my disposal, since you dont, i think that some sort of gasket paper,,,,,trace and make a tester gasket, test its compressed thikcness.
and torque it all the way.
m
one other thing is to measure how far down in the hole your pistons are when at TDC,,,,if they are recessed even .005 it will affect things,,,,,i want to know if they are flush, proud or recessed, but i want to know. if they are receessed too far to your liking you can have the tops of the cylinders machined,,,but it requires proper measurement to make sure that it comes out correctly.
i make solid lifters as well.
i use old gaskets when i am measuring, but i have them at my disposal, since you dont, i think that some sort of gasket paper,,,,,trace and make a tester gasket, test its compressed thikcness.
and torque it all the way.
m
one other thing is to measure how far down in the hole your pistons are when at TDC,,,,if they are recessed even .005 it will affect things,,,,,i want to know if they are flush, proud or recessed, but i want to know. if they are receessed too far to your liking you can have the tops of the cylinders machined,,,but it requires proper measurement to make sure that it comes out correctly.